Off-shore drilling apparatus



April 20, 1965 D. c. KOFAHL OFF-SHORE DRILLING APPARATUS Filed Oct. 16, 1961 3 W KW! m a 1 $1.. a 4 M p In: W E:

United States Patent 3,179,179 OFF-SHORE DRILLING APPARATUS David C. Kofahl, Bakersfield, Califl, assignor to Rrehfield Oil Corporation, Los Angeles, (Ialifi, a corporation of Delaware Filed Get. 16, 1961, Ser. No. 145,332 Claims. (Cl. 166-665) My present invention relates to off-shore drilling from a floating barge in relatively deep water and more particularly relates to oil-shore drilling apparatus wherein a longitudinally flexible slip-joint is utilized to allow for variation in the required length of the tubular drilling apparatus extending between a drilling barge and the ocean floor, during wave and tide action where the distance between the ocean floor and the barge varies.

Heretofore longitudinally flexible slip-joints, as shown in Reissue Patent No. 24,083, have been provided in the casing riser to prevent buckling or breaking when drilling operations are conducted from a floating barge in a formation underlying a body of water. A drilling head and blowout prevention equipment in such apparatus is normally positioned on the ocean floor for convenience and serviced by a diver. However, in relatively deep water where the ocean floor is below diving depths, it has been proposed to position the blowout preventer at or near the surface of the water, as at the drilling barge. The positioning of the drilling head at the surface of the water was common practice in drilling operations conducted from off-shore platforms where longitudinally flexible joints are not used since the distance between the platform and the well-head does not vary with tide or wave action. However, where a longitudinally flexible slipjoint is positioned below a blowout preventer on a floating drilling vessel system, closing the blowout preventer rams around the drill pipe, as with a large increase in drilling fluid pressure, tends to create hydraulic thrust within the casing riser which thrust tends to elongate the slip-joint and hold it in such elongated condition as long as the drilling fluid is subjected to the increased pressure. Hence, with the blowout preventer rams closed, the slipjoint tends to act like a large piston rather than a slipjoint unless there is some means for balancing the hydraulic thrust within the riser itself, which thrust prevents the slip-joint from working when pressure is put on the slip-joint with the blowout preventer rams closed.

Accordingly, it is an object of the present invention to balance the hydraulic thrust created within the casing riser where a blowout preventer is positioned over a longitudinally flexible joint and the sealing rams of such blowout preventer are closed around the drill pipe.

It is also an object of the present invention to provide a system for balancing the hydraulic thrust within a casing riser when a blowout preventer positioned over a telescopic slip-joint has the rams thereof closed, by providing flexible and automatic means for independently operating the telescopic joint.

Other objects and a more complete understanding of my present invention may be had by reference to the following specification taken in conjunction with the appended claims and the drawings, in which,

FIGURE 1 shows one form of the present invention in schematic form in a cross-sectional view of an oil-shore drilling barge operatively connected over a submarine drilling site.

FIGURE 2 is an enlarged section of the blowout preventer 36 showing the manner in which the sealing rams 37 seal around the drill pipe 18.

FIGURE 3 is an enlarged elevational view of telescopic slip-joint 3h.

3,179,179 Patented Apr. 20, 1965 FIGURE 4 is a sectional elevation of a modification of the apparatus shown in FIGURE 1.

Briefly described, my present invention relates to a method and apparatus for balancing the hydraulic thrust created within the casing riser when a blowout preventer with closed rams is positioned over a telescopic slipjoint and high drilling fluid or mud pressure prevails within the casing riser, whereby the mud pressure is used to operate one or more mud driven pistons which tend to close the telescopic joint in response to an increase in mud pressure. An increase in pressure in the riser tends to open the telescopic joint when the blowout preventer rams are closed. Hence the hydraulic thrust within the riser created by the increased mud pressure, which thrust would tend to open the slip-joint and prevent it from serving their normal function, is counter-balanced by closing the slip-joint in response to the buildup of mud pressure so that the slip-joint will continue working when subjected to high mud pressure in the drilling arrangement utilized in my present apparatus.

Referring to the drawings, in FIGURE 1, a drilling barge id is shown floating on a body of water 12 and positioned over the formation 14 into which drilling operations are conducted from the barge through a bore hole 16 with a drill pipe 18. A drilling base 29 is positioned at the formation over the well bore and drilling operations conducted therethrough. After the conductor pipe 22 and the surface casing 24 are run into the hole through the drilling base 2%), a casing riser Z6 is landed on the upper end of the surface casing and has provided therein swivel joints 28 to provide lateral flexibility in the surface riser and a slip-joint 30 to provide longitudinal flexibility in the casing riser 26. These apparatuses are of conventional design and are disclosed more fully in copending application No. 19,722, of W. D. Leake, filed April 4, 1960. Primary blowout prevention equipment 35 is positioned at the barge 10 over the access well 32 thereof and is supported on a sub-structure 34. This primary equipment 35 may consist of a conventional blowout preventer assemblage, such as a hydraulically controlled gate 36, shown in detail in FIGURE 2, and a bag type Hydril blowout preventer 38. The blowout prevention equipment 35 is positioned at the drilling barge to permit ready access thereto for repair and part replacements. Additional blowout preventers 40 and 42 may be posi tioned at or near the formation to provide blowout protection while the primary blowout prevention equipment i being repaired or is otherwise out of service. In deep water these blowout prevention gates 40 and 42; are preferably hydraulically or electrically operated through cable 44 which extends to the barge.

Drilling mud is pumped down through drill pipe 18 and into the formation in a conventional manner and returns to the barge through the annulus between the drill pipe and the casing riser 26, and thence to the mud-treating equipment (not shown) from the riser annulus above the primary blowout prevention equipment 35. The casing riser 26 is provided with an outlet 46 which is connected to the high pressure mud return line 43 which may also serve as a drill line. A pressure responsive valve 47 in line 48 is actuated in response to very high mud pressure in the riser annulus.

A riser T fitting 50 is positioned in the riser between the blowout preventer 36 and the slip-joint 30, to convey the annulus mud pressure through hoses 52 and 54 to mud driven pistons or rams housed within cylinders 58 which are mounted on the drilling barge 10. The lower member 3% of the slip-joint 3d is independently supported on cable line lit) with support brackets 62 afixcd to the outer (lower) member 30a of the slip-joint 30, as best shown in FIGURE 3.

The cables 6% are anchored at one end with anchors 64 and at the other end from pulley support 67 and extend around the fixed overhead pulley members 65 so that the lower or outer member of the telescopic joint 36 can be raised, that is, closed by extending the wire cable 6%) as with mud driven rams 7t) and 72. Extension of the wire cable to close slip-joint 30, may be accomplished by driving the rams '70 and 72 outwardly by the by draulic mud pressure exerted through cylinder piston members. The amount of lift transmitted to the slip-joint 30 may be controlled by the design of the piston area and the internal area of the riser, since the mud pressure in the riser and the piston area together equal the internal area of the riser. Thus an increase in mud pressure within the riser annulus causes the pistons within the cylinders 58 to actuate the rams 7i? and 72 and hence tend to raise lower member of slip-joint 39 so that any tendency of the hydraulic thrust within the riser to cause bowing of the riser and opening of the slip-joint 30 and thus prevent the slip-joint from working properly With increased pressure on it, is counterbalanced by the tendency of rams 7i and 72 to raise or close the slip-joint proportionately.

Hydraulically operated auxiliary rams (not shown) may be employed to operate the slip-joint 30 when there is no pressure on the rams 7t) and 72.

The hydraulic thrust created by high mud pressure in the riser when the blowout preventer 36 is closed, may also be counter-balanced by the apparatus shown in FIG- URE 4 which is an alternate embodiment of my present invention. With this apparatus the increased mud pressure in the riser 26 drives annular piston 843 which is connected to the lower portion 3% of the slip-joint by circumferentially spaced piston rods 82, upward to counter-balance the tendency of the slip-joint 30 to elongate with increased mud pressure. Mud passes into an annular cylinder 84 which is aflixed to the upper end 3 of the slip-joint 30, through outlets 86.

It is to be understood, of course, that the hydraulic thrust within the riser is created only when the rams of I the blowout preventer as are closed around the drill pipe, as shown in FIGURE 2. Otherwise the mud pressure is dissipated into the mud tanks. Mud may be pumped through the kill line 73 through either the riser annulus or the high pressure return hose 48 by the setting of the valves 74 and 76.

Although I have described my present invention in considerable detail in order to set forth the best contemplated mode of operation, it is to be understood that the scope of my invention is not to be so limited but should be afforded the full breadth of the appended claims.

I claim:

1. Apparatus for drilling or completing a well in a formation underlying a body or" water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having sealing rams movable within a housing to close the upper end of said tubular apparatus about said drill string, said tubular apparatus including a longitudinally flexible joint having an upper and a lower part, said upper and lower parts being longitudinally movable with respect to each other, said upper part being supported from said housing of said blowout preventer, and means tending to lift said lower part relative to said upper part in response to an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed.

2. Apparatus for drilling or completing a well in a formation underlying a body of Water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preenter having sealing rams movable within a housing to close the upper end of said tubular apparatus about said drill string, said tubular apparatus including a longitudinally flexible join-t having an upper and a lower part, said upper and lower parts being longitudinally movable with respect to each other, said upper part being supported from said casing of said blowout preventer, means for supporting said lower part independently from said upper member, and means tending to lift said lower part relative to said upper part in response to an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed.

3. The apparatus of claim 2 wherein said means for supporting said lower part is connected to said barge.

4. Apparatus for drilling or completing a well in a formation underlying a body of water from a drilling barge having an access opening therein through which a drill string may be extended, comprising in combination: a blowout preventer supported in said access opening, tubular apparatus extending from said Well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having sealing rams movable within a housing to close the upper end of said tubular apparatus about said drill string, said tubular apparatus including a longitudinally flexible joint having an upper and a lower part, said upper and lower parts being longitudinally movable with respect to each other, said upper part being supported from said housing of said blowout preventer, means for supporting said lower part independently from said upper member, and means tending to lift said lower part relative to said upper part in response to an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed about said drill string.

5. Apparatus for drilling or completing a well in a formation underlying a body of water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having rams movable within a housing to seal the upper end of said tubular apparatus around said drill string, said tubular apparatus including a longitudinally flexible joint having upper and lower parts, said upper and lower parts being longitudinally movable with respect to each other, and said upper part being supported from said housing of said blowout preventer, means for supporting said lower member independently of said upper member, and means cooperating with said independent support means for counter-balancing the hydraulic thrust within said tubular apparatus created by an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed around said drill string.

6. The apparatus of claim 5 wherein said counter-balancing means comprises a hydraulically driven ram, means for placing said rams in fluid communication with said drilling fluid, said ram being actuated by said drilling fluid.

7. Apparatus for drilling or completing a well in a formation underlying a body of water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having rams movable within a housing to seal the upper end of said tubular apparatus around said drill string, said tubular apparatus including a longitudinally flexible joint having an upper and a lower part, said upper and lower parts being longitudinally movable with respect to each other, and said upper part being supported from said housing of said blowout preventer, cable means connected to said barge for supporting said lower part independently of said upper part, and means actuated by an increase in the return drilling fluid pressure for controlling tension in said cable support means to counterbalance the hydraulic thrust within said tubular apparatus created by an increase in pressure on said drilling fluid within said tubular apparatus when said blowout preventer rams are closed around said drill string.

8. Apparatus for drilling a well bore in a formation underlying a body of water from a drilling barge through which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid conirnunication between said well and said barge through said blowout preventer, said blowout preventer having rams movable within a housing to seal the upper end of said tubular apparatus around said drill string, said tubular apparatus including a longitudinally flexible joint having upper and lower parts, said upper and lower parts being longitudinally movable with respect to each other, and said upper part being supported from said casing of said blowout preventer, means for supporting said lower member independently from said upper member, and means tending to lift said lower part relative to said upper part in response to an increase in pressure on said drilling fluid within said tubular apparatus when said blowout preventer rams are closed around said drill string.

9. Apparatus for drilling or completing a well in a formation underlying a body of water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said Well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having rams movable within a housing to seal the upper end of said tubular apparatus around said drill string, said tubular apparatus including a longitudinally flexible joint having upper and lower parts, said upper and lower parts being longitudinally movable with respect to each other, and said upper part being supported from said housing of said blowout preventer, and means for counter-balancing the hydraulic thrust within said longitudinally flexible joint created by an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed around said drill string.

10. Apparatus for drilling or completing a well in a formation underlying a body of water from a drilling barge from which a drill string may be extended, comprising in combination: a blowout preventer supported from said barge, tubular apparatus extending from said well to said blowout preventer, said tubular apparatus providing fluid communication between said well and said barge through said blowout preventer, said blowout preventer having rams movable within a housing to seal the upper end of said tubular apparatus around said drill string, said tubular apparatus including a longitudinally flexible joint having upper and lower parts, said upper and lower parts being longitudinally movable with respect to each other, and said upper part being supported from said hosuing of said blowout preventer, said upper part defining an annular cylinder atfixed to said tubular apparatus, said tubular apparatus having annularly spaced ports therein adjacent said upper part whereby drilling fluid from said tubular apparatus may enter said annular cylinder, an annular piston within said annular cylinder, operably connected to said lower part whereby said piston is urged upwardly in said cylinder when a predetermined drilling fluid pressure in said tubular apparatus is exceeded to thereby counter balance the hydraulic thrust within said tubular apparatus created by an increase in drilling fluid pressure within said tubular apparatus when said blowout preventer rams are closed around said drill string.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,083 11/55 McNeill -7 2,945,677 7/60 Kammerer 175-5 3,017,934 1/62 Rhodes et a1. 166-66 X CHARLES E. OCONNELL, Primary Examiner. 

1. APPARATUS FOR DRILLING OR COMPLETING A WELL IN A FORMATION UNDERLYING A BODY OF WATER FROM A DRILLING BARGE FROM WHICH A DRILL STRING MAY BE EXTENDED, COMPRISING IN COMBINATION: A BLOWOUT PREVENTER SUPPORTED FROM SAID BARGE, TUBULAR APPARATUS EXTENDING FROM SAID WELL TO SAID BLOWOUT PREVENTER, SAID TUBULAR APPARATUS PROVIDING FLUID COMMUNICATION BETWEEN SAID WELL AND SAID BARGE THROUGH SAID BLOWOUT PREVENTER, SAID BLOWOUT PREVENTER HAVING SEALING RAMS MOVABLE WITHIN A HOUSING TO CLOSE THE UPPER END OF SAID TUBULAR APPARATUS ABOUT SAID DRILL STRING, SAID TUBULAR APPARATUS INCLUDING A LONGITUDINALLY FLEXIBLE JOINT HAVING AN UPPER AND A LOWER PART, SAID UPPER AND LOWER PARTS BEING LONGITUDINALLY MOVABLE WITH RESPECT TO EACH OTHER, SAID UPPER PART BEING SUPPORTED FROM SAID HOUSING OF SAID BLOWOUT PREVENTER, AND MEANS TENDING TO LIFT SAID LOWER PART RELATIVE TO SAID UPPER PART IN RESPONSE TO AN INCREASE IN DRILLING FLUID PRESSURE WITHIN SAID TUBULAR APPARATUS WHEN SAID BLOWOUT PREVENTER RAMS ARE CLOSED. 